UPDATED: Palin Set For Keystone State Blitz

(DES MOINES, IOWA) - Sarah Palin is set to embark on an extensive bus tour of Pennsylvania next week, CBS News has learned.

Although recent polls show the Republican ticket trailing by double digits in the state, the McCain campaign appears to be largely resting its hopes for Election Day victory on a come-from-behind win in Pennsylvania.

Palin's Pennsylvania tour is set to begin on Tuesday in Harrisburg and Hershey. She is then scheduled to return to Missouri - a red state that the Republicans must win - before heading back to Pennsylvania for several other campaign stops, including one in Erie, according to a campaign source.